BsLPMO10A from Bacillus subtilis boosts the depolymerization of diverse polysaccharides linked via 8-1,4-glycosidic bonds

Lytic polysaccharide monooxygenase (LPMO) is known as an oxidatively cleaving enzyme in recalcitrant poly-saccharide deconstruction. Herein, we report a novel AA10 LPMO derived from Bacillus subtilis (BsLPMO10A). A substrate specificity study revealed that the enzyme exhibited an extensive active-substrate spectrum, particu-larly for polysaccharides linked via 8-1,4 glycosidic bonds, such as 8-(Man1-* 4Man), 8-(Glc1-* 4Glc) and 8-(Xyl1-* 4Xyl). HPAEC-PAD and MALDI-TOF-MS analyses indicated that BsLPMO10A dominantly liberated native oligosaccharides with a degree of polymerization (DP) of 3-6 and C1-oxidized oligosaccharides ranging from DP3ox to DP6ox from mixed linkage glucans and beechwood xylan. Due to its synergistic action with a variety of glycoside hydrolases, including glucanase IDSGLUC5-38, xylanase TfXYN11-1, cellulase IDSGLUC5-11 and chitinase BtCHI18-1, BsLPMO10A dramatically accelerated glucan, xylan, cellulose and chitin saccharifi-cation. After co-reaction for 72 h, the reducing sugars in Icelandic moss lichenan, beechwood xylan, phosphoric acid swollen cellulose and chitin yielded 3176 +/- 97, 7436 +/- 165, 649 +/- 44, and 2604 +/- 130 mu mol/L, which were 1.47-, 1.56-, 1.44-and 1.25-fold higher than those in the GHs alone groups, respectively (P < 0.001). In addition, the synergy of BsLPMO10A and GHs was further validated by the degradation of natural feedstuffs, the co-operation of BsLPMO10A and GHs released 3266 +/- 182 and 1725 +/- 107 mu mol/L of reducing sugars from Oryza sativa L. and Arachis hypogaea L. straws, respectively, which were significantly higher than those produced by GHs alone (P < 0.001). Furthermore, BsLPMO10A also accelerated the liberation of reducing sugars from Celluclast (R) 1.5 L, a commercial cellulase cocktail, on filter paper, A. hypogaea L. and O. sativa L. straws by 49.58 % (P < 0.05), 72.19 % (P < 0.001) and 54.36 % (P < 0.05), respectively. This work has characterized BsLPMO10A with a broad active-substrate scope, providing a promising candidate for lignocellulosic biomass biorefinery.

Automated summary

We report a novel AA10 LPMO enzyme derived from Bacillus subtilis (BsLPMO10A) with an extensive substrate specificity, especially for polysaccharides linked via 8-1,4 glycosidic bonds. Through synergistic action with various glycoside hydrolases, BsLPMO10A dramatically accelerates the saccharification of glucan, xylan, cellulose, and chitin. This study provides a promising candidate for lignocellulosic biomass biorefinery.